Electronic system distinguishing between good knots and defects in a moving strand

ABSTRACT

Two photocell detectors are spaced along a path of a moving strand with a gap of known fixed distance therebetween. The photocells view a length of the strand on each side of a knot or defect in the strand when the knot is presented in the gap. An inspection cycle is started by entry into the detectors of a knot or defect and a defective knot or defect is determined by comparing the dynamic signal status of a photocell spaced some distance behind the knot with the signal taken from a photocell ahead of the defect and stored. The existence of a signal at this position or of an exceptionally large signal indicated by comparison at the time of initiation of the cycle indicates the presence of a defective knot.

Erhstein ELECTRONIC SYSTEM DISTINGUISHING BETWEEN GOOD KNOTS AND DEFECTSIN A MOVING STRAND Inventor: Robert S. Erbstein, Coventry, R.1.

Assignee: Leesona Corporation, Warwick, RI.

Filed: May 19, 1972 Appl. No.: 255,178

US. Cl 340/259, 28/64, 73/160 Int. Cl D011 13/22 Field of Search.....340/259; 19/.21, .23; 28/64; 250/219 DF, 219 S; 356/238, 200; 66/16373/160;

References Cited UNITED STATES PATENTS 3/1968 Felix 28/64 10/1963 Ricra1/1971 Seymour, Jr. et al.. 5/1971 Harvey et al. 73/160 T IZ CUTTER 2'0i| so 7 137 1,3 l6 5 s ill, X i l 4 T Io 18 ,l .5 l4 KNOTTER PrimaryExaminerDonald J. Yusko Assistant ExaminerGlen R. Swann, 111

Attorney, Agent, or FirmAlbert P. Davis; Burnett W. Norton [5 7 ABSTRACT1 Two photocell detectors are spaced along a path of a moving strandwith a gap of known fixed distance therebetween. The photocells view'alength of the strand on each side of a knot or defect in the strand whenthe knot is presented in the gap.

An inspection cycle is started by entry into the detectors of a knot ordefect and a defective knot or defect is determined by comparing thedynamic signal status of a photocell spaced some distance behind theknot with the signal taken from a photocell ahead of the defect andstored. The existence of a signal at this position or of anexceptionally large signal indicated by comparison at the time ofinitiation of the cycle indicates the presence of a defective knot.

11 Claims, Drawing Figures TO CUTTER TIME DELAY minimum smI 3795306SIILEI 2 0F 4 OUTPUT OF AMP 2I r- -v lo 1 TP T P I OU u oFAM 20 L I 200I L ll OUTPUT OF AMP 23 OUTPUT OF AMP 24 l I OUTPUT OF AMP 27 OUTPUT OFPS 32 OUTPUT OF AMP 29 l I I I I l l I l l I l I OUTPUT OF 05 36 OUTPUTOF AMP 30 OUTPUT OF GATE 4I -I I (T037) PATENTEDIAR 51914 3795906 SNEI 30F 4 FIG. 3

ELECTRONIC SYSTEM DISTINGUISHING BETWEEN GOOD KNOTS AND DEFECTS IN AMOVING STRAND BACKGROUND OF THE INVENTION This invention relates toelectronic apparatus for detecting defects along a moving strand, andmore particula rly it relates to apparatus distinguishing between goodknots provided by a knotter mechanism and defects in a moving yarn.

THE PRIOR ART In textile machinery such as yarn winders it is customaryto produce large bobbins from a number of smaller bobbins. Automaticknotting mechanisms are used for piecing together the ends of the yarnsuch as obtained from two smaller bobbins or otherwise in order to makea continuous strand on the large bobbin. It is, therefore, desirable tomonitor the knotting mechanism to assure that a good knot is tied, andfurthermore, it is desirable to monitor the strandto cut out defectiveportions such as slubs which may have no relationship to the knotter. Ingeneral, textile equipment using the large bobbins can process a goodknot or a short thin slub or other strand defect, but must not receivethick slubs, doubled or wild yarn or long defects that would foulneedles or cause a defective fabric. Particularly for doubled yarn it isdifficult to distinguish by amplitude of a detected signal the defectiveareas while handling yarns that may have different diameters from timeto time. Also, a good knot may trigger an amplitude sensitive defectdetector depending upon the position of the loose tails.

In addition, a detection device should not be time sensitive and requireintegration or such techniques, since a good knot may be presented whilethe yarn is accelerating. Therefore, prior art devices have not reliablydistinguished between good knots and other nonaccep table defects whichhave some of the characteristics of good knots.

OBJECTS OF THE INVENTION Accordingly, his a general object of thisinvention to provide an improved defect detector operable with a movingstrand of various dimensions and changing speeds.

A further object of this invention is to provide improved detectormethods-and apparatus for distinguishing reliably between good knots andthe unwanted strand defects.

THE DRAWINGS ing of waveforms used'in operation of the various circuitsof FIG. 1.

DETAILED DESCRIPTION The general operationprinciple of the detectionsystem afforded in one embodiment of this invention may be observed byreference to FIG. 1. To process a strand, hereinafter termed yarn 12, aknotter 15 is provided such as that described in U. S. Pats. Nos.2,670,230 and 3,314,620 issued respectively to W. V. Goodhue et al. onFeb. 23, 1954 and T. E. Pitts et al. on Apr. 18, 1967. The strand 12passes in the direction of the arrow 14 so that a knot 13 may pass cell10 at a time T the gap 16 at the time T and the cell 11 at the time T Aregion of the strand passing the gap 16 before the knot is identified asX and a region passing the gap 16 after the knot is identified as Y.Preferably, the spacing d of the gap 16 is just enough to pass a goodknot 13 with its trailing tails 13a passing the first cell 10 when theknot is presented to the second cell 11.

The system afforded by this invention, therefore, should pass goodknots, but should detect bad knots which have tails which are too longor which have other strand defects such as doubles, wild yarn and slubseither while the yarn 12 is passing at substantially constant speedbetween knots or while accelerating after a knot 13 is tied by knotter15. Accordingly, the system should be relatively speed insensitivewithin these different strand speed limits.

To distinguish the good knots 13 from unwanted defects, the twophotocells 10, 11 are spaced with a gap 16 therebetween, and thus,sequentially observe the strand thickness along yarn 12 by means of asuitable optical array including preferably a single light source 17 andsome suitable lens and slit system 18. Thus, in the position shown foryarn 12 and knot 13, the photocell 10 will observe the region Y behindthe knot 13 and the photocell 11 will observe the region X ahead of theknot 13 at the time T at which the knot is within the-gap 16. The gap 16has a spacing d of such length that when a good knot 13 enters cell 11no significant part of it remains within the view of cell 10.

To prevent obscuring the nature of the invention with electronic circuitdetails, the circuits are shown in single line block diagram form. Thoseunits within the blocks are currently available in units such asintegrated circuit chips and the like, which may be interconnected bythose skilled in the art to provide appropriate interlock connectionsand voltages, etc., in the normal course of routine work.

In general, the system operates to inspect the strand when a knot ordefect along the strand triggers an inspection cycle. Initially, yarnmay be placed on cells 10 and 11, without triggering a cyclefby movingit in parallel to the axis of yarn travel into view of both cells. 10

and 11 simultaneously so that they see the same relative signals. Theinformation relating to region X as read by cell 11 is stored atcapacitor 22 when the knot or defect 13 passes cell 10 at time T Shoulda signal be observed during this comparison of cell 10 to cell 11 whichexceeds threshold level L, then an error condition is indicated and apulse stretcher 43 is energized which maintains a signal long enoughto-initiate cutter C to complete a cutting cycle.

If this threshold levelL, is not exceeded, the knot or defect willcontinue to cell 11 at which time threshold level L, at amplifier 29will be exceeded indicating the existance of a knot or defect at cell11. and not at cell 10. The output from amplifier 29 will initiate aninspection cycle during which the output 20a of amplifier 20 and thestored information are compared. To insurethat when a good knot isviewed at cell 11 no good tails,

etc., exist at cell 10, the occurrence of the interrogation signal 36ais delayed by time delay 37.

During the interrogation period signals of very short duration, as mayoccur from fuzz on the yarn, are blocked by time delay 38. Conversely,if during the inspection period a signal is passed through differentialamplifier 23 which exceeds threshold level L at amplifier 30 and time tset at time delay 38, then pulse stretcher 43 is energized to operatethe cutter, thereby cutting out the bad knot.

Thus, the system of FIG. 1 processes signals identifying the strandthickness detected at different positions along the length of the strandby photodetector cells 10, 11. Detected signals derived at differenttimes T and T are compared to thereby identify defects along the strandat the knot 13 and over region X ahead of the knot 13 and region Ybehind the knot.

Amplifiers 20 and 21 are high impedance amplifiers which have unity gainisolating photodetector cells and 11 respectively, and provide on busleads a and 21a dynamic signals identifying strand thicknesscharacteristics detected at the respective photocell locations providinginputs to the following circuits.

The relative timing of the waveforms to be discussed are shown in FIG. 2with reference to time periods T and T when the knot 13 passes cells 10and 11.

As the knot or defect passes cell 10 light is reduced so that the output20a of amplifier 20 falls below the output 210 of amplifier 21.Differential amplifier 23 subtracts the two signals and amplifies thedifference. Amplifiers 25 and 27 are threshold devices which compare theoutput of differential amplifier 23 to threshold levels L and Lrespectively as set by their respective potentiometers R and R Ifthreshold level L is exceeded then as mentioned earlier, the cutter isenergized. If threshold level L is exceeded and not level L, then theoutput of amplifier 27 switches from an off state 0 to an on state 1corresponding to the time threshold level L is exceeded. This triggerspulse stretcher 32 which de-energizes coil 35 opening contact 35a for aperiod of time greater than that required for the knot or defect toreach cell 11.

Upon reaching cell 11 at time T the output 21a of amplifier 21 dropsbelow the level stored on capacitor 22 and the difference between thesignals is amplified by differential amplifier 24. If the knot or defecthad been large enough to turn amplifier 27 on then amplifier 29 whichalso compares the output of amplifier 24 to threshold level L will turnon. In switching from an 0 to 1 state amplifier 29 sets one shot 36.This keeps switch 35a open for a period of time in excess of that set bypulse stretcher 32. After a time delay, designated TD37 in FIG. 2, whichis long enough to insure that an acceptable knot is not also viewed bycell 10, as set by time delay 37, signal 370 will interrogate the outputof amplifier through AND gate 41, providing the output of amplifier 30exceeds the time set by time delay 38. 1f the spacing between cells 10and 11 is large enough and the length of the fuzz to be eliminated issmall then the times associated with time delays 37 and 38 may be keptsufficiently small so as to keep the sensing relatively speedinsensitive.

The output of cell 11 (Amp. 21) in FIG. 2 is shown to remain lowindicating a long tail. Since under these conditions the output ofdifferential amplifier 23 exceeds threshold level L during theinterrogation cycle set by one shot 36 an output occurs at AND gate 41causing the cutter to cut out the defective knot.

It is to be noted that in addition to prohibiting a signal when the yarnis placed between cells 10 and 11, differentially connecting cells 10and 11 minimizes variation due to fluctuations in light level and yarnmovement providing the period of movement is large compared to thespacing between cells. Also, the dual cell and differentiatingarrangement removes errors due to lint which may accummulate on bothcells substantially evenly, and varying diameters of yarn or changes inambient light or temperature.

The field of view of the photocells l0, 1 1 also may be shaped to aiddetection of certain errors. If a long narrow cell area is presentedalong strand 12, then strand doubles may be detected while eliminatingshort defects or double yarn thickness, for example.

A diffuser lens scattering light from light source 17 can be used togenerate a uniform area of randomized light rays making strandorientation as viewed by cells 10, 11 less critical.

Other modes of comparison may be introduced to produce error signals ifsuch conditions of defective yarn occur where a fault precedes the knot13, i.e., the cell 11 signal is greater than that of cell 10.

In practice with the present invention if the speed of advance of strand12 is constant, then the intervals associated with time delays 37 and 38may be lengthened. This means that the relationship between theeffective spacing between cells 10 and 11 and length of knots or defectsto be detected by the cells can be set solely in terms of time.Furthermore if the time and consequently the length associated withdelay 38 is large compared to the effective spacing between cells 10 and11, time delay 37 becomes unnecessary thus simplifying the circuit.

What is claimed is:

1. Electronic apparatus processing a moving knotted strand such as yarnto detect defects therein and pass good knots comprising in combination,a pair of detection means sampling the strand at two positionssuccessively along its path of movement with a gap therebetween, meansresponsive to the entry of a knot or defeet when it enters a first ofsaid positions to initiate an inspection cycle, means storing a signalderived from the entry of a knot by one of said detection means, andmeans comparing. during said inspection cycle the stored signal with thecurrent signal being received from said strand by the other of saiddetection means to derive a defect signal upon a signal imbalance whenone of said signals is significantly greater than the other.

2. Apparatus as defined in claim 1 wherein the pair of detection meanscomprises a pair of photoelectric cells and including means detectingentry of the knot or defect at each of the cells and producing therefroma defect signal, and means eliminating the defect signal during the timethe defect is viewed only by the first detection means.

3. Apparatus as defined in claim 2 including a timing circuit generatinga signal used to control said means eliminating the defect signal, saidtiming circuit producing said signal a predetermined time after saiddefeet is first viewed by the second successive one of said detectionmeans.

4. Apparatus as defined in claim 3 including further timing means forprocessing said defect signal when said signal imbalance persists beyonda predetermined time.

5. Apparatus as defined in claim 1 wherein the comparing means includetiming means for producing the imbalance signal only when the defectpersists beyond a predetermined time span during which a good knot isexpected to pass.

6. Apparatus as defined in claim 5 including separate amplifyingchannels processing the signals from each detection means to providesignals to said comparison means.

7. Apparatus as defined in claim 1 wherein said stored signal is derivedfrom one of said detection means and the comparing means compares thestored signal with the current signal on the other detection means.

8. The method of distinguishing between a good knot and an unacceptabledefect in a moving strand such as yarn, comprising the steps of,detecting in a moving strand enlarged portions presented at a detectionstation, timing the duration of the presence of the enlarged portionsdetected, and producing an alarm only when the enlarged portions arepresent for a period beyond a predetermined time span approximating thetime span during which good knots pass said detection station.

9. The method defined in claim 8 wherein the step of detecting theenlarged portions of the strand includes sensing the strand at twosuccessive detection station positions along the path of movement of thestrand.

10. The method defined in claim 9 including the step of piecing up twobroken ends in a knotter away from said two successive positions andthereafter moving the pieced up strand into both said detection stationposi tions simultaneously.

11. The method defined in claim 8, wherein the detecting step includesimpinging diffused light on the moving strand and processing collimateddiffused light leaving the strand at said detection station.

1. Electronic apparatus processing a moving knotted strand such as yarnto detect defects therein and pass good knots comprising in combination,a pair of detection means sampling the strand at two positionssuccessively along its path of movement with a gap therebetween, meansresponsive to the entry of a knot or defect when it enters a first ofsaid positions to initiate an inspection cycle, means storing a signalderived from the entry of a knot by one of said detection means, andmeans comparing during said inspection cycle the stored signal with thecurrent signal being received from said strand by the other of saiddetection means to derive a defect signal upon a signal imbalance whenone of said signals is significantly greater than the other. 2.Apparatus as defined in claim 1 wherein the pair of detection meanscomprises a pair of photoelectric cells and including means detectingentry of the knot or defect at each of the cells and producing therefroma defect signal, and means eliminating the defect signal during the timethe defect is viewed only by the first detection means.
 3. Apparatus asdefined in claim 2 including a timing circuit generating a signal usedto control said means eliminating the defect signal, said timing circuitproducing said signal a predetermined time after said defect is firstviewed by the second successive one of said detection means. 4.Apparatus as defined in claim 3 including further timing means forprocessing said defect signal when said signal imbalance persists beyonda predetermined time.
 5. Apparatus as defined in claim 1 wherein thecomparing means include timing means for producing the imbalance signalonly when the defect persists beyond a predetermined time span duringwhich a good knot is expected to pass.
 6. Apparatus as defined in claim5 including separate amplifying channels processing the signals fromeach detection means to provide signals to said comparison means. 7.Apparatus as defined in claim 1 wherein said stored signal is derivedfrom one of said detection means and the comparing means compares thestored signal with the current signal on the other detection means. 8.The method of distinguishing between a good knot and an unacceptabledefect in a moving strand such as yarn, comprising the steps of,detecting in a moving strand enlarged portions presented at a detectionstation, timing the duration of the presence of the enlarged portionsdetected, and producing an alarm only when the enlarged portions arepresent for a period beyond a predetermined time span approximating thetime span during which good knots pAss said detection station.
 9. Themethod defined in claim 8 wherein the step of detecting the enlargedportions of the strand includes sensing the strand at two successivedetection station positions along the path of movement of the strand.10. The method defined in claim 9 including the step of piecing up twobroken ends in a knotter away from said two successive positions andthereafter moving the pieced up strand into both said detection stationpositions simultaneously.
 11. The method defined in claim 8, wherein thedetecting step includes impinging diffused light on the moving strandand processing collimated diffused light leaving the strand at saiddetection station.